In the wheel machining industry, wheel balance degree is an important factor affecting the comfort and the safety of an automobile and is a 100% test item. At the same time, the rejection rate of wheel balance out of tolerance is an important factor affecting the wheel yield. By research and analysis, the wheel balance out of tolerance may be caused by many factors, wherein the outer rim machining traces formed in the first and second procedures of the wheel machining process are the key factor of balance out of tolerance. The fixture of the present invention not only can realize no machining trace on a wheel outer rim and improve the balance precision of the wheel, but also can improve the machining effect on the outer rim.